{"id":"CVE-2026-84784","summary":"QUIC: Unbounded RETIRE_CONNECTION_ID Backlog","details":"Issue summary: A malicious remote peer may flood the local QUIC\nstack with NEW_CONNECTION_ID frames by avoiding a limit check on\nhow many connection IDs the remote QUIC stack can use.\n\nImpact summary: The local QUIC stack sends a RETIRE_CONN_ID frame\nfor every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_ID\nframe is dispatched via the Control Frame Queue (CFQ). If the remote\npeer also withholds ACKs, then it can force the local stack\nto allocate ~400MB (depending on ACK delay).\n\nCWE: CWE-770: Allocation of Resources Without Limits or Throttling\n\nDescription: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanism\nby which a remote peer can notify the local QUIC stack to change the\ndestination connection ID (a.k.a. CID) the local stack uses to\nidentify the connection at the remote peer. Each CID is associated\nwith a sequence number. The sequence number is transmitted\nin NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CID\nwhich is being either associated with a connection or retired.\n\nThe remote peer sends a NEW_CONNECTION_ID frame to let the local stack know\na new CID is being associated with an existing connection. The\nNEW_CONNECTION_ID frame carries the new CID, its sequence number, and the\nretire-prior-to number. The retire-prior-to identifies existing\nCIDs that are to be retired. The local QUIC stack must send a\nRETIRE_CONNECTION_ID for every destination CID whose sequence number\nis less than retire-prior-to. The CID becomes retired after the\nlocal stack receives an ACK for its RETIRE_CONNECTION_ID frame.\n\nAlthough the OpenSSL QUIC stack supports at most one destination CID\nfor every connection, it can be tricked into processing more than\none RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUIC\nstack currently retires the destination CID as soon as it receives\nthe NEW_CONNECTION_ID, while in fact the destination CID must\nbe retired after an ACK for the RETIRE_CONNECTION_ID frame is received.\nCorrecting the flawed logic also fixes the backlog growth.\n\n[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids\n\nFIPS impact: no\nThe FIPS module is not affected as the QUIC implementation is outside of\nthe OpenSSL FIPS module boundary.","modified":"2026-09-30T03:50:01.621822539Z","published":"2026-09-29T15:32:25.758Z","database_specific":{"cna_assigner":"openssl","cwe_ids":["CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84784.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84784.json"},{"type":"FIX","url":"https://github.com/openssl/openssl/commit/4685c914b0d410b1034f40b547c95bc95e7a380a"},{"type":"FIX","url":"https://github.com/openssl/openssl/commit/9a30fe0fba195c14e5b87bf93c0d0fdb70373806"},{"type":"FIX","url":"https://github.com/openssl/openssl/commit/dba3c48d653c64fcbc9070a17a0ee2b3e2f3af1f"},{"type":"FIX","url":"https://github.com/openssl/openssl/commit/e9e5155833fa968bee50024bf9ca3a185ab599fe"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84784"},{"type":"ADVISORY","url":"https://openssl-library.org/news/secadv/20260929.txt"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/openssl/openssl","events":[{"introduced":"11b7b6ea3b65a584e1d31408ed1bdb139465cffd"},{"fixed":"af1775b60dfa141a4ad762585052cabeb9f37e9e"},{"introduced":"7b371d80d959ec9ab4139d09d78e83c090de9779"},{"fixed":"c8bd5a57108599ac650bbae77fcabe3109dab2e8"},{"introduced":"636dfadc70ce26f2473870570bfd9ec352806b1d"},{"fixed":"45e844fa2a14ec92d146bd8f5778ac130b6625fb"},{"introduced":"98acb6b02839c609ef5b837794e08d906d965335"},{"fixed":"e72c946f6f6d94c8ba5119acb25340b7b6b2073f"}],"database_specific":{"extracted_events":[{"introduced":"4.0.0"},{"fixed":"4.0.3"},{"introduced":"3.6.0"},{"fixed":"3.6.5"},{"introduced":"3.5.0"},{"fixed":"3.5.9"},{"introduced":"3.4.0"},{"fixed":"3.4.8"}],"source":"AFFECTED_FIELD"}}],"versions":["openssl-3.4.7","openssl-3.5.8","openssl-3.6.4","openssl-4.0.2","openssl-3.4.6","openssl-3.5.7","openssl-3.6.3","openssl-4.0.1","openssl-4.0.0","openssl-3.4.5","openssl-3.5.6","openssl-3.6.2","openssl-3.4.4","openssl-3.5.5","openssl-3.6.1","3.4-POST-CLANG-FORMAT-WEBKIT","3.4-PRE-CLANG-FORMAT-WEBKIT","3.5-POST-CLANG-FORMAT-WEBKIT","3.5-PRE-CLANG-FORMAT-WEBKIT","3.6-POST-CLANG-FORMAT-WEBKIT","3.6-PRE-CLANG-FORMAT-WEBKIT","openssl-3.6.0","openssl-3.4.3","openssl-3.5.4","openssl-3.5.3","openssl-3.5.2","openssl-3.4.2","openssl-3.5.1","openssl-3.5.0","openssl-3.4.1","openssl-3.4.0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-84784.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}